My attempt to replace a hose bibb (3/4") was not successful due to very tight access to the connecting pipe ( attachment hose.bibb.JPG.) Luckily, the other side of the wall is the garage. After cutting out the wall panel, I find out the other end of the pipe the bibb connected has undergone some severe corrosion (attachment pipe.JPG.) and I can feel some moisture around the corrosion. Also a ground copper wire is attached to this pipe.

I'd like to tap this forum for its collected wisdom and advice to tackle such task, prior to finalize how to proceed with replacing the hose bibb and the pipe.
Here are some of the questions I have:
1) What is a recommended way to chisel out the cement around the pipe behind the hose bibb?
2) The house was built in the 70s. Is replacing the 90-degree elbow (attachment pipe.JPG.) also the right thing o do, when the pipe and bibb are replaced?
3) Should the ground wire be attached to other part of the pipe system, before the defected parts are taken out.
4) Regarding threading the pipe to get a water-tight connection, I vaguely recall there is a rule of thumb on keep turning until about 3 to 4 threads exposed. Any advice on best practice and cautions to maximize the success of getting a water-tight connection will be appreciated.

1. There is no "good" way. You have to do whatever is necessary.
2. The elbow is fine as it is
3. The ground wire is also fine where it is
4. Forget any "formula". You tighten it is as much as you can, and if it leaks, you tighten it some more.

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You would do well to have someone familiar with house wiring to check out the purpose of that "ground" connection. For one
thing, the pipe clamp appears to be of a type used on telephone and other low-voltage wiring, and not approved for use in a house
electrical system. For another, all grounding connections of that type are required to remain accessible, and not buried in a wall as that
one appears to be. All-in-all, a very dubious setup.

It does look like a galvanized pipe and it never should be used for any kind of grounding. There is just too much resistance to earth ground. You're in San Francisco, CA and perhaps the building code requires this type of pipe for strength through masonry, however, most homes build in the early part of the 20th century did use galvanized pipe before copper came easily and cheaply available in the 1950's. The electrical building ground is usually grounded at the main water line coming through the foundation wall of the home and/or a ground rod is driven into the ground. The location of yours is really perplexing. Cable and telephone companies will usually ground their equipment with there own ground rod or to an easily accessible cold water copper pipe. Obviously this ground clamp was installed before the bricks went up. Also, this ground wire does look like it is a #8 gauge wire that are used for AC electrical ground and not low voltage equipment. If it is your house ground connection, do not remove it with the main breaker turned on. And if you do not know what it is, get an electrician. You can have goofy things happening in your electrical system with a poor ground. Most likely your home is grounded with a ground rod and this ground wire grounds the plumbing for the house and they are tie together in the circuit panel.